Conventionally, hydraulic cylinders have been used to move a tail stock and apply pressure to a work, as described in Patent Document 2 for example (description on “tail stock 526” and “cylinder 527” in FIG. 1 and a paragraph [0027]). Thus, the control of the movement and pressure application has been predicated on the use of hydraulic cylinder.
However, in use of a hydraulic cylinder a large space is required to install, for example, a cylinder mechanism and an oil pressure circuit, etc.
Moreover, the hydraulic cylinder also requires complicated and cumbersome operations for the control because the pressure force applied to the work is adjusted by a manual pressure reducing valve and because the change in oil pressure is slow. Hence, the hydraulic cylinder is not suitable for speedy control.
For example, Patent Document 1 proposes a structure of sliding a tail stock with a ball screw (description on “tail stock 21” and “ball screw device” in FIG. 1 and the paragraph [0010]), to replace the method using the hydraulic cylinder having the technical problems described above. However, in Patent Document 1, a specific structure related to a control mechanism for moving the tail stock with the ball screw and applying pressure to the work, is not described at all.